二刷75. Sort Colors

Medium
counting sort的方法不说了，比较简单，直接上partition那个方法, 用two pointers. 把0全部赶到左边，2赶到右边，要注意每次变化之后指针怎么变： left, right, i都分别怎么变

class Solution {
    public void sortColors(int[] nums) {
        int left = 0;
        int right = nums.length - 1;
        int i = 0;
        while (i <= right){        
            if (nums[i] == 0){
                swap(nums, i, left);
                left++;
                i++;
            } else if (nums[i] == 2){
                swap(nums, i, right);
                right--;
            } else {
                i++;
            }
        }    
    }
    
    private void swap(int[] nums, int i, int j){
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }
}